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| author | Victor Stinner <vstinner@redhat.com> | 2019-04-12 19:27:37 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2019-04-12 19:27:37 (GMT) |
| commit | 23a683adf803eef405d248cc9c2a7eb08a7300e2 (patch) | |
| tree | 6e2c3cfbe541c098b51418c092bc8e61a20937ab /configure.ac | |
| parent | 606c66a17faf34a4e74d4829e8fe5ad0d2879434 (diff) | |
| download | cpython-23a683adf803eef405d248cc9c2a7eb08a7300e2.zip cpython-23a683adf803eef405d248cc9c2a7eb08a7300e2.tar.gz cpython-23a683adf803eef405d248cc9c2a7eb08a7300e2.tar.bz2 | |
bpo-36618: Add -fmax-type-align=8 flag for clang (GH-12809)
Add -fmax-type-align=8 to CFLAGS when clang compiler is detected.
The pymalloc memory allocator aligns memory on 8 bytes. On x86-64,
clang expects alignment on 16 bytes by default and so uses MOVAPS
instruction which can lead to segmentation fault. Instruct clang that
Python is limited to alignemnt on 8 bytes to use MOVUPS instruction
instead: slower but don't trigger a SIGSEGV if the memory is not
aligned on 16 bytes.
Sadly, the flag must be expected to CFLAGS and not just
CFLAGS_NODIST, since third party C extensions can have the same
issue.
Diffstat (limited to 'configure.ac')
| -rw-r--r-- | configure.ac | 41 |
1 files changed, 28 insertions, 13 deletions
diff --git a/configure.ac b/configure.ac index 30e8587..863b342 100644 --- a/configure.ac +++ b/configure.ac @@ -1464,6 +1464,19 @@ esac # compiler and platform. BASECFLAGS tweaks need to be made even if the # user set OPT. +case $CC in + *clang*) + cc_is_clang=1 + ;; + *) + if $CC --version 2>&1 | grep -q clang + then + cc_is_clang=1 + else + cc_is_clang= + fi +esac + # tweak OPT based on compiler and platform, only if the user didn't set # it on the command line AC_SUBST(OPT) @@ -1477,19 +1490,6 @@ then WRAP="-fwrapv" fi - case $CC in - *clang*) - cc_is_clang=1 - ;; - *) - if $CC --version 2>&1 | grep -q clang - then - cc_is_clang=1 - else - cc_is_clang= - fi - esac - if test -n "${cc_is_clang}" then # Clang also needs -fwrapv @@ -1530,6 +1530,21 @@ then esac fi +if test -n "${cc_is_clang}" +then + # bpo-36618: Add -fmax-type-align=8 to CFLAGS when clang compiler is + # detected. The pymalloc memory allocator aligns memory on 8 bytes. On + # x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS + # instruction which can lead to segmentation fault. Instruct clang that + # Python is limited to alignemnt on 8 bytes to use MOVUPS instruction + # instead: slower but don't trigger a SIGSEGV if the memory is not aligned + # on 16 bytes. + # + # Sadly, the flag must be expected to CFLAGS and not just CFLAGS_NODIST, + # since third party C extensions can have the same issue. + CFLAGS="$CFLAGS -fmax-type-align=8" +fi + AC_SUBST(BASECFLAGS) AC_SUBST(CFLAGS_NODIST) AC_SUBST(LDFLAGS_NODIST) |